Stable support of different anisotropic "armored bubbles" with various particle sizes and bubble sizes. (a) Ellipsoidal bubble obtained by fusing two spherical armored bubbles. (b) Extremely high aspect-ratio gas bubbles such as these mm-length spherocylinders can be formed by several successive coalescence events. (c) A membranelike solid created by partially evacuating an armored bubble that was originally spherical. (d) One can even generate a permanent stable change in topology of an air bubble by introducing a hole to create a toroid.

Experiments have shown that if a fluid-fluid interface is covered with particles that are sterically jammed, the interface can exist in stable non-spherical shapes. The jammed particles thus allow the interface to behave in some ways like a solid. In this article, the authors examine the effects of small homogeneous and inhomogeneous stresses on this granular medium, or "armored bubble". They characterize the armored interface as an interfacial composite material because the interfacially trapped particles retain their individual characteristics.